The long-range goal of this project is to develop expanded porphyrin-based drugs for the treatment of human disease. To date, much of the focus has centered on the so-called texaphyrins. As the result of considerable effort, involving the P.l.'s group, the co-P.I. and other researchers at Pharmacyclics, Inc., a cadre of dedicated clinicians, and Cooperative Research and Development (clinical) support from the NCI, the gadolinium(lll) complex of a water solubilized texaphyrin, motexafin gadolinium (MGd;XcytrinZ(r)), has emerged as an agent with considerable promise in the area of cancer therapy, especially for non-small lung cancer (NSCLC). This agent, which is known to localize well to tumors, is currently the subject of more than a dozen ongoing clinical trials, including ones targeting metastatic brain tumors, non-Hodgkin's lymphoma, renal cell carcinoma, glioma, head and neck cancer, juvenile glioma, and NSCLC. In this context, MGd is being studied as both an adjuvant for radiation therapy and as a stand-alone chemotherapeutic, where it is being administered on its own or with other anticancer agents. Given this state of development, the goals for the upcoming funding period are two-fold: First, to support the clinical trials by continuing mechanistic studies of MGd and, second, to develop yet-improved drugs. Key questions we will address include: What are the relative effects of redox cycling, reactive oxygen species (ROS) production, and perturbations in zinc homeostasis in mediating the effect of MGd? Can analogues of MGd be generated that show improved chemical properties, including redox cycling capability? Do these systems lead to enhanced anti-cancer activity in vitro as judged by cellular assays and, if warranted, in vivo tumor regrowth studies? What are the factors that regulate the cellular- and sub-cellular localization of MGd and its analogues? Can these localization properties be exploited to generate carriers that deliver other active agents, including known oncology drugs, to cancer sites? Can approaches other than those based on MGd be used to modulate the intracellular concentrations of zinc ion and, if so, how are such perturbations reflected in anticancer activity? The proposed work will lead to progress in the anticancer area and provide a basis for rational drug design.